measurement of peripapillary retinal nerve fiber layer thickness by three-dimensional optical coherence tomography in an iranian population

purpose: to determine peripapillary retinal nerve fiber layer (rnfl) thickness by three-dimensional optical coherence tomography (3d-oct) in a normal iranian population and to evaluate the concordance of these measurements with those obtained by the second generation of optical coherence tomography (oct ii). methods: in a cross-sectional observational study, 96 normal iranian subjects 20-53 years of age were enrolled. peripapillary rnfl thickness in one randomly selected eye of each subject was measured by 3d-oct and also by oct ii. standard achromatic perimetry, corneal pachymetry and a-scan ultrasonographic biometry were also performed. other study variables included age, gender, laterality (right versus left eye), refractive error, corneal diameter and disc area. results: mean peripapillary rnfl thickness measured by 3d-oct (75.50±8.38 µm) was significantly less than that measured by oct ii (144.10±33.32 µm) (p<0.001). using 3d-oct, no significant difference in peripapillary rnfl thickness was observed by gender (p=0.90) or laterality (p=0.17); rnfl thickness had no correlation with age (p=0.95), axial length (p=0.32), spherical equivalent refractive error (p=0.21), central corneal thickness (p=0.66) and disc area (p=0.31). however, a positive correlation was found between peripapillary rnfl thickness and corneal diameter (p=0.03). conclusion: 3d-oct seems to yield lower rnfl thickness values as compared to oct ii. it seems advisable to obtain separate baseline measurements when using different generations of oct machines.